EMBRYOLOGICAL SKETCH.
These rudiments consist of the primi tive kidneys or Wolffian bodies and their excretory ducts, which early de velop from the lateral plates adjoining the primitive vertebrEe. To these are added later on and on their inner side, the two Miillerian ducts. In the fifth week, on the inner side of the Wolffian bodies, and closely ad joining them, the rudiments of the sexual glands are developed, which for some time do not indicate whether they will be of the male or female kind. As soon as the sex is determined, which is shown by a change in the form, position, and principally in a differentiation in the internal structure, the formation of the permanent generative organs is continued, in that only a part of the above-described rudimentary layers is utilized, while the other part remains rudimentary or completely disappears. The peculiarity of this is that the part, which is further developed in males, remains stationary in females and vice versa. If the development does not proceed in this way, but parts develop which should remain station ary, or if others are arrested in their growth instead of progressing to complete development, those hybrid formations are produced which are difficult to distinguish sexually, so that very often cause is given for doubt.
If the sexual glands have become converted into the testicles, these gradually become united with the excretory ducts of the Wolffian bodies. This canal forms itself into the lower part of the epididymis, the sper matic duct and vesicle, but the Wolffian bodies are partly changed into the head of the epididymis, while the Mullerian ducts almost entirely disappear and only remain in scanty rudiments, as the vesieula, prostatiea or masculine uterus. If the sexual glands are changed into the ovaries, then the Milllerian ducts are further developed, and their upper portions become changed into the tubes, and their middle and lower portions are blended, so that the septa between the two canals disappear and the com mon cavity becomes changed into the uterus and the vagina; the Wolffian body- remains rudimentary and appears later as the Parovarium, while its excretory duct in mankind almost disappears, and is only met with as Giirtner's duct.